What happens with mental ray?

[lobopaco]

Hello,

I'm just asking me why mental ray has become soooo much slower with increasing version number...

FOr example. my lightbulb scene (www.3dartist.f2s.com/scene_lightbulb.jpg) renders 5 min 32 sec in Softimage 3.7 (mental ray 1.?) and with exactly the same settings, Soft 3.9.1 (mental ray 2.1) takes 21 mins 13 secs. No, I didn't use GI or Final Gathering. I just open the scene and render it. It looks identical, but renders 4 times longer. Also other scenes are slower, although the difference is smaller.

Andillo

[pomme]

In reply to:
Hello,

I'm just asking me why mental ray has become soooo much slower with increasing version number...

FOr example. my lightbulb scene (www.3dartist.f2s.com/scene_lightbulb.jpg) renders 5 min 32 sec in Softimage 3.7 (mental ray 1.?) and with exactly the same settings, Soft 3.9.1 (mental ray 2.1) takes 21 mins 13 secs. No, I didn't use GI or Final Gathering. I just open the scene and render it. It looks identical, but renders 4 times longer. Also other scenes are slower, although the difference is smaller.

Andillo

Well, i never compared the 2. however, 21 mins are really long. How many lights do you got in your scene. From where i see, I think is 2-3 lights. And 21 mins are really too long. How about the reflection, is it a mr reflection? I mean is it reflecting the scene itself? or just a reflection map. But either why. This is taking too long. I thing there has some settings have been changed by SI. Check them out.

[devdoka]

A few questions:

• Are you rendering on the same machine? If so, are both v3.7 and v3.9.1 installed on the machine or is one installed across the network and the other local?

• Set the renderer in v3.9 to use mr v1.9, do you still get the slowdown?

There are a few possible reasons why it takes longer to render:

1) Mental ray v1.9 (as used in v3.7) and mental ray v2.1 (as used in v3.8SP2 and later) interpret some of the render settings differently. What is efficient in v1.9 isn't necessarily efficient in 2.1. One example of this is the acceleration method, you may want to try Grid mode in mr 2.1 instead of BSP for your lightbulb.

2) When importing a scene from an older version of SI3D, not all scene settings are properly recognized. This is especially true with shaders. If you have an inactive shader somewhere in the scene when saved out of v3.7, it may become active when loaded in say v3.8. Lens and volume shaders can add significant time to your renders if not kept in check. Check all the scene's shader stacks as well as all render options.

3) Paths. When importing scenes, you have to make sure all your paths are defined correctly leading to your bitmaps and other external data. Not doing so may cause SI3D to hunt around the network until it finds the material (even if it ends up using local data). This will slow rendering greatly.

More info would be helpful

Matt

---

Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com

[lobopaco]

Hello again,

• the lightbulb scene uses only one light (!!) (spot), without area lights
• the stuff reflecting in the glass is only a raytraced reflection map from a PIC file
• the mental ray settings in BOTH SI 2.7 and 3.9 are: refl. 2, refr.2, sum 4, also the antialiassing is identical
• I'm rendering on the same machine, but I never install 3.9 + 3.9 together, I just tried it before Windows reinstall...
• I didn't use any shaders in my scene (like lens shader or so...) only simple 2D textures and one raytraced refl. map
• Paths: I always run it from one database where all PICs are. No network stuff or so.
  -which other settings could have been changed by SI 3.9.1?

BTW, I also tried out my other scenes on a P3-1000 MHz(www.3dartist.f2s.com) and here are the results (first is SI 3.9.1, second is SI 3.7):

Glassware: 17m 25s / 11m 46s
Lightbulb: 21m 13s / 5m 32s
Banana: 7m 07s / 3m 47s
Tea Time: 9m 05s / 9m 39s (faster in 3.9.1!!!)

[devdoka]

@- the mental ray settings in BOTH SI 2.7 and 3.9 are: refl. 2, refr.2, sum 4, also the antialiassing is identical

what about the other settings?

@- I'm rendering on the same machine, but I never install 3.9 + 3.9 together, I just tried it before Windows reinstall...

Aha! here's the problem - you haven't done an apples to apples test. You used v3.7 on the original installation of windows while using v3.9 on a re-install. In order for these test renders to mean anything, you have to do the tests for both v3.7 and v3.9 under the same conditions. I bet there's a network gremlin in there somewhere.

@- Paths: I always run it from one database where all PICs are. No network stuff or so.

To mental ray, all paths are absolute, so whether they're on the local machine or across a network makes no difference. If any of the drive names changed or were modified not quite right by either you or Softimage|3D, then some unnecesary could certainly be introduced.

@-which other settings could have been changed by SI 3.9.1?

Quite a few, but I wouldn't tinker with any of them until some apples-to-apples test renders are performed. You're gonna have to put v3.7 back on the machine in order to do this.

@BTW, I also tried out my other scenes on a P3-1000 MHz(www.3dartist.f2s.com) and here are the results (first is SI 3.9.1, second is SI 3.7):

Something's wrong here, these times don't match those listed on the website.

Matt

---

Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com

[lobopaco]

"what about the other settings?" -> Which settings, can you be more exact?

By the way, I also tried a FRESH Windows+Softimage 3.7 installation against FRESH Windows+Softimage 3.9... same results

"Something's wrong here, these times don't match those listed on the website."
-> Yes, because the render-times from my website are created by my Pentium3-700MHz and the comparison here is a Pentium3-1GHz against Athlon-1GHz which I had to evaluate for a week. That should explain the difference.

Andillo

[devdoka]

@ "what about the other settings?" -> Which settings, can you be more exact?

All of them.

@By the way, I also tried a FRESH Windows+Softimage 3.7 installation against FRESH Windows+Softimage 3.9... same results

Pull out the installation disks and install mr v1.9 with v3.9, this should bring out some answers. If mr 1.9 in v3.9 is slower than mr 1.9 in v3.7, then there's something wrong with 3.9 or your installation of 3.9.

Matt

---

Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com